1. Field of the Invention
This invention relates to a blade cleaning device usable in the electrophotographic copying apparatus or the like, and more particularly to such a blade cleaning device which is prevented from vibrating during a cleaning operation.
2. Description of the Prior Art
As the cleaning device for cleaning the photosensitive medium or the like in electrophotographic apparatuses, the fur brush cleaning device or the web cleaning device has heretofore been proposed and put into use.
A typical example of the former device is disclosed in U.S. Pat. No. 2,832,977, and a typical example of the latter device is disclosed in U.S. Pat. No. 3,186,838. Both of these devices can accomplish practical cleaning. Nevertheless, the former device suffered from scattering of removed toner and necessitated the provision of an absorption collector equipped with a dust collecting filter such as a vacuum cleaner for absorbing scattered toner and moreover, the toner so collected was trapped in the dust collecting filter within the absorption collector and could not practically be reused. The latter device required means for transporting a web to be urged against the photosensitive medium, and was apt to impart damages to the surface of the photosensitive medium, which in turn led to frequent needs to replace the photosensitive medium. Furthermore, the web surface became abraded during cleaning and the removed toner was trapped between the fibers of the web and could not be reused in practice.
To overcome the various problems peculiar to these types of cleaning devices, a novel type of cleaning device known as the blade cleaning device has been proposed and put into practice. The technique pertaining to such blade cleaning device is disclosed in U.S. Pat. No. 3,438,706 issued to Hiroshi Tanaka et al., and its improved techniques are disclosed in U.S. Pat. No. 3,859,691 issued to Hajime Katayama et al., U.S. Pat. No. 3,927,936 issued to Shigehiro Komori et al. and U.S. Pat. No. 3,917,398 issued to Toru Takahashi et al.
In the blade type cleaning device, a blade is urged against the surface of a member to be cleaned, practically such as a photosensitive medium, to effect cleaning, but stick slip vibration tends to occur at the area of contact between the blade and the cleaned member and such stick slip vibration has sometimes caused vibration of particularly great amplitude understandable as an oscillation phenomenon to be induced in the blade cleaning portion comprising the blade and its holder shaft. Such vibration has produced a sound which has become unpleasant noise to the user.
Moreover, such vibration could be transmitted to other units of the apparatus to adversely affect the quality of copy image, including the formation of a blurred image, and further to cause loosening of the set screws for various units.
The aforementioned stick slip vibration is considered attributable to the friction characteristic in the area of contact between the blade and the photosensitive medium which results from the quality of the material and roughness of the surface of the photosensitive medium and the quality of the material and roughness of the blade, and various methods for preventing occurrence of such phenomenon in the cleaning device have been studied heretofore. However, only U.S. Pat. No. 3,552,850 discloses a method using an antifriction material which may be regarded as an effective method and as far as the inventor knows, there has been disclosed no technique directed to the solution of the stick slip vibration in an electrophotographic apparatus.
Moreover, the stick slip vibration is closely related to the friction characteristic in the area of contact between the drum surface and the blade, as already noted, and various factors are considered to be so complexly correlated with such friction characteristic that it is difficult to eliminate the stick slip vibration only by the use of the aforementioned antifriction material, for example. The use of such antifriction material affects the cleaning performance and may further affect the surface characteristic of the photosensitive medium to produce blur in the formed image, thus making it very difficult to obtain a good result.